Coil assembly

ABSTRACT

An improved coil for use such as a degaussing coil in color television receivers. The coil is formed in a novel manner by causing the winding of the coil wires to form the annular bobbin from a strip of flexible channel material. The strip is maintained in an annular configuration by the wire causing its reception in an annular groove defined by a pair of axially spaceable arbor portions. The arbor portions further define means for holding the end of the wire upon initiation of the coilforming operation. The bobbin is preferably formed of a thermoplastic material suitable to be sealed by radio frequency energy permitting the legs of the bobbin channel to be secured together about the coil. The bobbin is discontinuously annular and a portion of the coil may bridge the gap between the opposite ends of the bobbin. Connector portions of the wire are brought out to externally of the bobbin, at least one connector portion being brought out through the gap. Improved means are provided for delivering the radio frequency sealing energy to the bobbin.

United States Patent [191 Gharaibeh [451 Apr. 15, 1975 COIL ASSEMBLY [75] Inventor: Hashem M. Gharaibeh, Palatine, 111.

[73] Assignee: Warwick Electronics Inc., Chicago,

[22] Filed: June 20, 1974 [21] Appl. No.: 481,350

Related US. Application Data [62] Division of Ser. No. 24l,53l, April 6, 1972.

[52] U.S. Cl. 336/208; 336/209; 336/229 [51] Int. Cl. H0lf 27/30 [58] Field of Search 29/596, 605; 242/708,

[56] 7 References Cited UNITED STATES PATENTS 1,504,733 8/1924 Angier et al 336/209 X 3,671,906 6/1972 Hodges et a1. 336/208 Primary ExaminerThomas J. Kozma Attorney, Agent, or Firm--Wegner, Stellman, McCord, Wiles & Wood [5 7 ABSTRACT An improved coil for use such as a degaussing coil in color television receivers. The coil is formed in a novel manner by causing the winding of the coil wires to form the annular bobbin from a strip of flexible channel material. The strip is maintained in an annular configuration by the wire causing its reception in an annular groove defined by a pair of axially spaceable arbor portions. The arbor portions further define means for holding the end of the wire upon initiation of the coil-forming operation. The bobbin is preferably formed of a thermoplastic material suitable to be sealed by radio frequency energy permitting the legs of the bobbin channel to be secured together about the coil. The bobbin is discontinuously annular and a portion of the coil may bridge the gap between the opposite ends of the bobbin. Connector portions of the wire are brought out to externally of the bobbin, at least one connector portion being brought out through the gap. Improved means are provided for delivering the radio frequency sealing energy to the bobbin.

9 Claims, 14 Drawing Figures PATEFHEB APRI 5 I95 sum 2 o g con. ASSEMBLY CROSS-REFERENCE TO RELATED APPLICATIONS This application comprises a division of copending application Ser. No. 241.531. filed Apr. 6. 1972.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to coil assemblies and in particular to relatively large diameter coil assemblies such as for use as degaussing coils for color television receivers.

2. Description of the Prior Art One prior art electrical coil as shown in U.S. Pat. No. to Freeman et al. 3.443.136 includes a pair of oppositely spaced insulating liners in a channel defined outwardly by a removable plate. The liners are retained in the channels by holding one side as by a clip and blowing air against the other side. The liners are laid in the channel prior to the winding of the coil therein.

In the U.S. Pat. to Gartner No. 2.399.631. a coil is wound on an adhesive coated sheath which is closed on itself upon completion of the winding of the coil. The sheath is formed by impaling the opposite ends thereof on a plurality of pins whereby the sheath ends overlap to form a continuous annular strip.

Other prior art U.S. Pat. Nos. relating to coil forming include Cammauf 3.063.136. Wuczkowski 3.046.509. Korte 2.400.008. and Penn 3.202.950. cited in the parent case hereof.

SUMMARY OF THE INVENTION The present invention comprehends an improved coil assembly wherein a channel element formed of a suitable material sealable by heat is formed into an annular configuration by the action of the placement of the wire in the channel in association with an annular arbor. One end of the strip is held to the arbor adjacent the end of a wire supply and the arbor is then rotated to cause a laying down of the wire in the radially out wardly opening channel and concurrently urge the channel into an annular groove in the arbor. Upon completion of one turn. the wire holds the channel in the arbor groove in the desired annular bobbin configuration. permitting further turns of the arbor to be effected suitably for laying down additional turns of the coil. The channel and arbor groove may have engagement of preselected shoulders for maintaining the radially outwardly opening arrangement of the channel in the groove while yet permitting the internal cross section of the channel to be round and thereby facilitate forming of the coil therein. The legs of the channel may be maintained spaced apart adjacent the delivery of the wire thereinto to assure proper feed of the wire in the coil-forming operation.

After a small number of turns have been applied to assure proper retention of the channel in the annular bobbin configuration in the arbor groove. the speed of rotation of the arbor may be increased so as to increase the rate of coil formation. The final winding of the coil may be preselected so as to terminate short of an integral number of turns as desired. Upon completion of the winding of the desired coil. sealing elements may be brought into engagement with the channel legs to urge them together and concurrently effect sealing thereof by provision of heat energy thereto. The invention comprehends an improved sealing assembly construction for providing radio frequency energy uniformly along the length of the legs to effect the seal. As indicated above. one of the electrical connections may be brought out spaced from the gap between the opposite ends ofthe channel and. thus. an opening in the sealed leg structure may be provided at that point.

The end of the wire may be held at the start of the coil winding operation by the use of an axially split arbor having frictional portions adapted to clamp the wire end therebetween when the split portions are urged together at the start of the coil-forming operation. The split arbor portions may jointly define the desired annular groove in which the channel is received to form the bobbin and. thus. upon separation of the arbor portions at completion of the coil assembly operation. the annular coil assembly may be removed radially through the gap between the axially spaced arbor portions. as the held wire end is released concurrently. The means for delivering the wire into the channel as it is being rotated on the arbor may comprise a delivery head having a depending guide adapted to fit between the channel legs and maintain the channel legs spaced apart to assure proper delivery of the wire into the channel. Upon completion of the coil-forming step. the delivery head is automatically retracted to permit the desired sealing together of the leg portions.

To provide the desired uniform radio frequency energy to the channel legs. a pair of sealing assemblies is provided wherein the radio frequency energy is delivered to segmentally spaced annular portions thereof by means of a feeder bus structure conducting the radio frequency energy to the separate plate segments. The bus includes a first arcuate distributor portion connected to less than all of the segments and a second arcuate distributor portion connected to the remaining segments and to at least one of the segments to which the first distributor is connected. The two distributors may be on opposite faces of the sealing assembly and a radial portion may extend from one ofthe distributors for connection thereof to the power supply or ground as desired.

BRIEF DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will be apparent from the following description taken in connection with the accompanying drawing wherein:

FIG. 1 is a fragmentary front elevation of an apparatus for forming an improved coil assembly embodying the invention;

FIG. 2 is a fragmentary front elevation thereof as upon initiation of the sealing operation;

FIG. 3 is an enlarged cross section of the bobbin at a position forwardly of the wire feed guide upon winding of an initial number of turns thereon in the apparatus;

FIG. 4 is an enlarged cross section similar to that of FIG. 3 but with the bobbin sealed closed about the coil as during the sealing step;

FIG. 5 is a fragmentary perspective view of the apparatus illustrating the feed of the wire and the bobbin strip into association with the apparatus as upon initiation of the coil-forming operation:

FIG. 6 is a fragmentary perspective view illustrating the start of the coil-forming operation:

FIG. 7 is a fragmentary enlarged vertical section taken substantially along the line 77 of FIG. 6;

FIG. 8 is a side elevation of the heat sealing means:

FIG. 9 is a fragmentary vertical section illustrating further the securing of the wire and strip ends at the initiation of the coil-forming operation;

FIG. 10 is a fragmentary vertical section illustrating the arrangement of the bobbin and wire upon completion of the winding of the first turn:

FIG. I1 is a side elevation of the completed coil:

FIG. 12 is an end elevation thereof:

FIG. [3 is a fragmentary front elevation of an alternate form of the apparatus; and.

FIG. 14 is a fragmentary enlarged cross section taken along lines 14l4 of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the exemplary embodiment of the invention as disclosed in the drawing. an apparatus generally designated 10 is shown for providing an improved coil assembly in a novel improved manner. In illustrating the invention. it will be considered that the coil assembly defines a relatively large diameter coil such as a de gaussing coil for use in a color television receiver. it being understood that the invention comprehends other suitable coils embodying the novel invention concepts as disclosed and claimed herein.

Apparatus 10 for forming the improved coil assembly includes a wire feed head 11 which is selectively moved from a retracted position to a feeding position as shown in FIG. I for delivering a wire 12 to between a pair of axially split arbor portions I3 and 14. The righthand arbor portion 13 is axially fixed while the lefthand arbor portion 14 is axially movable to and from the arbor portion 13. Arbor portion 13 is rigidly affixed to a shaft I5, while arbor portion 14 is rotatably mounted at 16 to a shaft '17. Any suitable means. such as a hydraulic cylinder (not shown). may be used to effect axial movement of shaft 17 and. hence. determine the position of arbor portion 14.

Thus. as shown in FIG. 2. when arbor portion 14 is brought into facial engagement with arbor portion 13. the arbor portions effectively define an arbor 18 having a radially outwardly opening circumferential groove 19. The arbor portions 13 and 14 are provided with frictional surfaces 20 which fixedly clamp the end 21 of the wire 12 when the arbor portions are brought together. A clip 22 is provided on arbor portion 13, as shown in FIG. 5. for receiving the end of a channel strip 23. Thus. as shown in FIG. 6, when the arbor portions 13 and 14 are brought together with the wire end 21 held therebetween. the leading strip end 24 is inserted into the groove 19 to engage the clip 22 so that the end 24 is disposed within the groove 19 closely adjacent the wire end 21.

Strip 23 effectively comprises a channel element formed ofa flexible electrically insulating material such as a thermoplastic. The length of the strip is preselected to be slightly less than the annular length of the groove 19 so that the distal end 25 of the strip is spaced slightly from the first end 24, as shown in FIG. 10. when the strip is received inthe groove 19 in a corresponding annular configuration. The strip is caused to be received in the groove 19 by the wire 12 as a result of the laying of the wire into the channel strip. More specifically, upon insertion of the strip end 24 into the clip 22., as shown in FIG. 9, the arbor 18 is rotated in a counterclockwise direction as seen therein whereby the wire enters into the channel strip 23 and urges the channel strip downwardly into the groove 19. Upon one complete turn of the arbor. as shown in FIG. 10, the strip 23 effectively defines a discontinuously annular bobbin having a gap 26 between ends 24 and 25. Continued rotation of the arbor in the counterclockwise direction effects the winding of additional turns of wire in the channel bobbin as illustrated in FIG. 3. To facilitate placement of the wire in the channel. a depending guide 27 is provided on head I] maintaining the legs 28 and 29 of the channel strip 23 spaced apart adjacent the clip 22. As shown in FIG. 3. strip 23 defines an externally squared cross section including corner shoulder portions 30 which cooperate with the squared groove corner shoulder portion 30a to prevent twisting of the channel strip in the groove and maintain the channel opening accurately outwardly during the coil winding operation. The channel strip 23 further defines a circular cross section internal configuration which causes the completed coil to have a circular cross section as shown in FIG. 4.

As shown in FIG. 3, the channel legs 28 and 29 terminate in flat outer portions 31 and 32. The channel leg portions 31 and 32 extend outwardly from the groove 19 so that upon completion of the winding of the coil 33 in the arbor channel. the leg portions 3I and 32 may be sealingly joined by the urging together thereof effected by a pair of opposed annular flanges 34 and 35 associated with a pair of axially spaced sealing assemblies 36 and 37. respectively. As shown in FIG. 4. the flanges force the opposed leg portions 31 and 32 into facial engagement to effectively close the channel 23 about the wound coil. The leg portions may be autogenously bonded together as by use of radio frequency energy transmitted through the flanges 34 and 35.

The sealing assemblies 36 and 37 are similar in construction. As shown with reference to FIGS. 8 and I4. the sealing assemblies each comprise a segmentally annular construction formed of a plurality of sealing elements 38 spaced annularly apart and secured to a conductive back-up plate 39 which is correspondingly segmented. The segmented back-up plate 39 is secured to a nonconductive plate 60 which is not segmented. The gap 40 between the segmented portions of the sealing elements and between the corresponding portions of the back-up plate is preferably relatively small. illustratively such as one-sixteenth inch.

The members 38, 39. and of both sealing assemblies 36 and 37 are of annular construction so as to allow the appropriate one of the arbor shafts I5 and 17 to pass freely therethrough. Radio frequency energy is transmitted to the sealing elements through a bus structure generally designated 41, which includes a first arcuate distributor 42 overlying a number of the segmented sealing elements. The distributor 42 is positioned behind the conductive plate 39 and adjacent the nonconductive plate 60 such that the segmented sections of plate 39 are not contacted. In the illustrated embodiment. the distributor 42 is shown overlying approximately one-half of the sealing elements and extending arcuately approximately l. A second arcuate distributor comprising a pair of elements 43 and 44 is provided overlying the opposite surface of plate 39, the elements extending approximately l20each and being spaced apart approximately 60at their opposite ends symmetrically to the centerline of the first distributor 42, as shown in FIG. 8. The distributor elements 43 and 44 are connected at points intermediate their length to distributor 42 by conductive connecting means generally designated 45. In the embodiment shown. each of the connecting means 45 includes boss portions 47 surrounding an aperture 46 in plate 39 and a screw 48 which passes through distributor element 43 and threads into distributor element 42. Thus. distributor elements 42 and 43 are in electrical contact with each other and with the plate 39 at the connection means 45. Distributor elements 43 and 44 are connected to the various segments of plate 39 by conductive connecting means generally designated 45'. The construction of connection means 45 may be similar to that of connecting means 45 but for the fact that distributor element 42 has no connection with the plate 39 or the distributor elements 43 and 44 at these points. Thus. distributor element 42 supplies the radio frequency energy to the intermediate portions of distributor elements 43 and 44 which. in turn. distribute the energy to the various segments of the segmented plate 39 and hence. to the corresponding sealing elements 38. Screws such as that shown at 42 or other suitable fastening means may be used to secure the segments of plate 39 to the annular insulating plate 60. Similarly. the insulating plate 60 is secured to plate 54 by means of screws such as illustrated at 63.

A conducting means 49 is provided extending radially outwardly from distributor 42 for conducting radio frequency energy from a suitable source (not shown) to one of the sealing plates and for use in grounding the opposite sealing plate.

Axial movement of the sealing assemblies 36 and 37 and the resulting movement of flanges 34 and 35 into respective engagement with the leg portions 31 and 32 of the channel strip 23 is effected by means of hydraulic cylinders 50 and 51. respectively. la the embodiment of the apparatus shown in F165. 1 and 2, the hydraulic cylinders 50 and 51 are located coaxially with respect to the winding arbor shafts and 17. The movable members or pistons 52 and 53 associated with the hydrualic cylinders are hollow. surrounding their respective arbor shafts so as to permit relative axial movement therebetween. Pistons 52 and 53 are secured to plates 54 and 55. respectively. which carry the sealing assemblies 36 and 37. A pair of parallel guide bars 56 and 57 are secured to a pair of fixed brackets 58 and 59 as shown. and passed through diametrically opposed apertures in plates 54 and 55. The brackets 58 and 59 are rigidly secured to the base 61 for the apparatus. ln this manner. the movement of the sealing plates is carefully controlled to ensure an accurate meeting of the sealing elements during each sealing operation.

Alternatively. as shown in FIG. 13. in a second embodiment of the apparatus generally designated 110. the sealing members 136 and 137 may be rigidly secured to a pair of brackets 158 and 159. respectively. which are slidably carried on abase 161. Hydrualic cylinders 150 and 151 effect axial movement ofthe brack ets 158 and 159 and are affixed to the base 161 by means of appropriate supports such as illustrated at 190 and 191. The supports 190 and 191 also serve as mounting means for the shafts 115 and 117 associated with the winding arbor 118. A hydraulic cylinder 192 for effecting axial movement of arbor shaft 117 may also be mounted to support 191. Operationof hydraulic cylinders 150 and 151 causes brackets 158 and 159 to move along a path determined by guide members 193 and 194. which are affixed to the base 161 and configured so as to permit only movement along the axis of the sealing members 136 and 137.

As shown in FIG. 11. the leg portions of the bobbin channel are joined throughout the length of the bobbin except at spaced portions 64 aligned with the gaps 40 of the sealing plate where the bond will be of lesser strength. Flanges 34 and 35 may be provided with a notch to provide a gap 66 in the closed bobbin spaced from the gap 26 where the last turn of the coil is not a complete turn to permit bringing the finish end I 67 of the wire 12 outwardly through the bobbin.

Upon completion of the joining of the leg portions 31 and 32 of the bobbin to complete the enclosing of the coil 33, the wire feed head 11 retracts upwardly. the wire 12 is cut. and arbor portion 14 is retracted along its axis whereupon the bobbin may be disengaged from clip 22 and brought forwardly through the space between the arbor portions as the wire end 21 is also automatically released by the spacing of the arbor portions.

The rotation of the complete arbor 18 may be effected by rotatably driving the shaft 15 to which arbor portion 13 is affixed. thereby causing arbor portion 14 to rotate due to frictional engagement between the arbor portions. A suitable motor drive may be applied as shown at 68 and may be controlled by suitable automatic control equipment (not shown) to effect the desired operation of apparatus 10 to effect the formation of the coil as discussed above. lllustratively. the apparatus may be operated to effect rotation of the arbor at a relatively slow rate during the laying down of the first turn or several turns and effect a high speed winding of the remaining turns once the bobbin is firmly set in place in the arbor groove 19 and held therein by the wire. Where the last turn of the coil is less than a full turn. the gap 26 will be spaced downwardly from the uppermost position. However. the sealing plate gap 65 is fixed at the uppermost position in alignment with the end 67 of the wire and. thus. the opening 66 isautomatically positioned to accommodate the outward extension 67 of the wire. Thus. for example. a coil having a large number of full turns and a final fractional turn may be accurately and quickly formed. A suitable cutter (not shown) may be provided for cutting the wire upon completion of the sealing closure of the bobbin leg portions.

The use of the split arbor permits facilitated initiation of the coil winding operation while permitting ready removal of the completed coil. The depending wire end 21 need not extend directly veritcally downwardly as long as it extends between the frictional surfaces 20. Thus. guiding means are obviated while yet the wire end is positively held at the initiation of the coil winding operation. The use of the wire itself to form the annular bobbin from an effectively rectilinear channel strip permits high speed facilitated forming of the coil. The self-guiding action of portions 31 and 32 of the channel strip and the guide 27 combine to ensure an accurate laying down of the wire turns in the annularly arranged bobbin upon completion of the first turn of wire thereabout. The axial movability of the arbor portions and sealing plates facilitates the coil'forming operation while yet assuring positive accurate forming of the coil in the bobbin strip 23. It has been found that the use of apparatus 10 permits the forming of such coils with an operator having no special skills and permitting the operation by such an operator of a plurality of such machines concurrently as the need for manipulation of the apparatus and bobbin strip occurs only at the beginning and end of-the coil winding operation The resultant coil is relatively flexible. permitting the accommodation thereof to the cathode ray tube for degaussing operation. If desired. the gap 26 between the end portions of the bobbin may be scaled by a suitable closure strip (not shown) wrapped thereabout.

The segmented construction of the sealing members and the configuration of the RF energy distribution members associated therewith combine to permit uni- 1 form high quality sealing of the bobbin leg portions on each coil produced. The construction of the sealing members also permits facilitated changeover for accommodating bobbins of various diameters. in that the segmented sealing elements 38 may be removed from the segmented back-up plate 39 and replaced with an alternate set of such elements of a different size without disturbing the RF energy distribution system.

As will be obvious to those skilled in the art. by use of the axially split arbor. the channel strip may be provided originally in a complete annular form which is captured in the arbor groove when the arbor portions are brought together. Where such a continuously annular arbor strip is used. the clip 22 may be omitted and the wire end 21 may be brought down through a suitable opening in the bight of the channel to be received between the frictional wire engaging surfaces 20. In this case. the wire does not effect the forming of the annular configuration of the strip. but in all other respects. the forming of the coil is similar to the forming of coil assembly 52 discussed above.

The foregoing disclosure of specific embodiments is illustrative of the broad inventive concepts comprehended by the invention.

I claim:

1. A coil assembly comprising:

a bobbin comprising a discontinuous annulus having a radially inner wall. and side walls extending radially outwardly from the axially opposite ends of said inner wall and defining therewith a coil space having a gap defined by the discontinuity of the bobbin annulus; and

a continuously annular wound wire coil coaxially in said bobbin coil space bridging said bobbin gap and having connection portions for making electrical connections to said coil. said bobbin enclosing said coil substantially the entire annular length of the bobbin and being provided with an opening intermediate its ends. a first one of said connection portions extending outwardly through said gap and a second of said connection portions extending outwardly through said opening.

2. The coil assembly of claim 1 wherein said opening opens radially outwardly.

3. The coil assembly of claim 1 wherein said bobbin has a square external cross section and a circular internal cross section.

4. The coil assembly ofclaim I wherein said first connection portions extends radially inwardly from said coil.

5. The coil assembly of claim 1 wherein said first connection portion extends radially inwardly through said gap and said opening opens radially outwardly. whereby said second connection portion extends radially outwardly.

6. A coil assembly comprising:

a bobbin comprising a discontinuous annulus having a radially inner wall. and side walls extending radially outwardly from the axially opposite ends of said inner wall and defining therewith a coil space I having a gap defined by the discontinuity of the bobbin annulus: and

a continuously annular wound wire coil coaxially in I said bobbin gap and having connection portions for making electrical connections to said coil. said bobbin including radially outer leg portions joined together in a secured relationship to enclose the wound wire coil over substantially the entire length of the bobbin. the leg portions having a different association therebetween as compared to said secured relationship at spaced portions along the length of the bobbin. said portions having a small annular length such that the secured portions of the bobbin adjacent thereto maintain the legs effectively closed together at the spaced portions.

7. The coil assembly of claim 6 wherein the bobbin is formed of resilient material tending to expand from the annular configuration toward a rectilinear configuration and said wire coil retains the bobbin in the annular configuration against such expansion tendency.

8. The coil assembly of claim 6 wherein said bobbin is formed of a thermoplastic material and said legs are thermally fused together to provide said secured relationship.

9. The coil assembly of claim 6 wherein said leg portions are fused together to provide said secure relation,- ship at a position spaced substantially outwardly from said wire coil. 

1. A coil assembly comprising: a bobbin comprising a discontinuous annulus having a radially inner wall, and side walls extending radially outwardly from the axially opposite ends of said inner wall and defining therewith a coil space having a gap defined by the discontinuity of the bobbin annulus; and a continuously annular wound wire coil coaxially in said bobbin coil space bridging said bobbin gap and having connection portions for making electrical connections to said coil, said bobbin enclosing said coil substantially the entire annular length of the bobbin and being provided with an opening intermediate its ends, a first one of said connection portions extending outwardly through said gap and a second of said connection portions extending outwardly through said opening.
 2. The coil assembly of claim 1 wherein said opening opens radially outwardly.
 3. The coil assembly of claim 1 wherein said bobbin has a square external cross section and a circular internal cross section.
 4. The coil assembly of claim 1 wherein said first connection portions extends radially inwardly from said coil.
 5. The coil assembly of claim 1 wherein said first connection portion extends radially inwardly through said gap and said opening opens radially outwardly, whereby said second connection portion extends radially outwardly.
 6. A coil assembly comprising: a bobbin comprising a discontinuous annulus having a radially inner wall, and side walls extending radially outwardly from the axially opposite ends of said inner wall and defining therewith a coil space having a gap defined by the discontinuity of the bobbin annulus; and a continuously annular wound wire coil coaxially in said bobbin gap and having connection portions for making electrical connections to said coil, said bobbin including radially outer leg portions joined together in a secured relationship to enclose the wound wire coil over substantially the entire length of the bobbin, the leg portions having a different association therebetween as compared to said secured relationship at spaced portions along the length of the bobbin, said portions having a small annular length such that the secured portions of the bobbin adjacent thereto maintain the legs effectively closed together at the spaced portions.
 7. The coil assembly of claim 6 wherein the bobbin is formed of resilient material tending to expand from the annular configuration toward a rectilinear configuration and said wire coil retains the bobbin in the annular configuration against such expansion tendency.
 8. The coil assembly of claim 6 wherein said bobbin is formed of a thermoplastic material and said legs are thermally fused together to provide said secured relationship.
 9. The coil assembly of claim 6 wherein said leg portions are fused together to provide said secure relationship at a position spaced substantially outwardly from said wire coil. 